The present invention relates generally to biosynthetic processes and more specifically to organisms capable of using synthesis gas or other gaseous carbon sources and methanol.
Synthesis gas (syngas) is a mixture of primarily H2 and CO that can be obtained via gasification of any organic feedstock, such as coal, coal oil, natural gas, biomass, or waste organic matter. Numerous gasification processes have been developed, and most designs are based on partial oxidation, where limiting oxygen avoids full combustion, of organic materials at high temperatures (500-1500° C.) to provide syngas as a 0.5:1-3:1 H2/CO mixture. Steam is sometimes added to increase the hydrogen content, typically with increased CO2 production through the water gas shift reaction.
Today, coal is the main substrate used for industrial production of syngas, which is traditionally used for heating and power and as a feedstock for Fischer-Tropsch synthesis of methanol and liquid hydrocarbons. Many large chemical and energy companies employ coal gasification processes on large scale and there is experience in the industry using this technology.
In addition to coal, many types of biomass have been used for syngas production. Gaseous substrates such as syngas and CO2 represent the most inexpensive and most flexible feedstocks available for the biological production of renewable chemicals and fuels. During World War II, there were over 1 million small scale biomass gasification units in operation, mainly in Europe, for running cars, trucks, boats, and buses. Currently, there are at least three major biomass gasification technologies that have been or are in the process of being validated on a commercial scale (>20 million lb biomass/yr). Biomass gasification technologies are being practiced commercially, particularly for heat and energy generation. Integration with fuels or chemicals production is being developed and has not yet been demonstrated widely at a commercial scale.
Overall, technology now exists for cost-effective production of syngas from a plethora of materials, including coal, biomass, wastes, polymers, and the like, at virtually any location in the world. The benefits of using syngas include flexibility, since syngas can be produced from most organic substances, including biomass. Another benefit is that syngas is inexpensive, costing ≦$6 per million Btu, representing raw material costs of ≦$0.10/lb product. In addition, there are known pathways, as in organisms such as Clostridium spp., that utilize syngas effectively.
Despite the availability of organisms that utilize syngas, in general the known organisms are poorly characterized and are not well suited for commercial development. For example, Clostridium and related bacteria are strict anaerobes that are intolerant to high concentrations of certain products such as butanol, thus limiting titers and commercialization potential. The Clostridia also produce multiple products, which presents separations issues in obtaining a desired product. Finally development of facile genetic tools to manipulate Clostridial genes is in its infancy; therefore, they are not readily amenable to genetic engineering to improve yield or production characteristics of a desired product.
Thus, there exists a need to develop microorganisms and methods of their use to utilize syngas or other gaseous carbon sources for the production of desired chemicals and fuels. More specifically, there exists a need to develop microorganisms for synthesis gas utilization that also have existing and efficient genetic tools to enable their rapid engineering to produce valuable products at useful rates and quantities. The present invention satisfies this need and provides related advantages as well.